1. Field of the Invention
This invention relates to texturization processes for proteinaceous materials. More specifically, it relates to texturization of single-cell proteins and other powder-like protein products by solvent-induced coagulation.
2. Description of the Prior Art
Protein products are used in foods for their functionality as well as their nutritional value. The texture of a protein product contributes to its functionality as well as to its taste. Most vegetable protein products, e.g. soybean protein products, are in the form of powders or grits. A texturization technology has been developed to incorporate some textural characteristics to soybean proteins. One known process produces meat substitutes from edible protein materials by forming fibers or filaments and then, by suitable means, binding the fibers. These protein fibers are prepared from a spinning dope of protein which is forced through a porous membrane such as a spinneret to form fibers which are coagulated in a bath containing suitable acids and salts and are oriented by suitable means, such as by a series of rolls revolving at increasing speeds. The fibers are placed in a salt solution such as sodium chloride of sufficient concentration to prevent the fibers from dissolving.
Textured protein foods can also be produced without spinning. One such process involves the rapid orientation and coagulation of protein material in a substantially undenatured, finely-divided, hydrated state under conditions which produce a shred-like structure. Orientation and coagulation of protein must be coordinated so that coagulation follows orientation of the molecules, whereby upon the action of the coagulation influence the molecules are set in a shred-like condition. The process is conducted with about 50% slurry of the protein material in water. The slurry is rapidly heated to and maintained at 360.degree. F. for about 1 minute in an autoclave and cooled rapidly. A shredded meatlike texture is obtained.
In various other processes mixtures of proteins are used in which one of these proteins serves as a binder. In such mixtures gluten or egg white is used as a heat coagulating ingredient to set the extruded or shredded protein textures.
In another process a chewy gel is prepared by (a) adjusting the composition of a protein-water system, in particular the pH and the solids content, to a composition conducive to gel formation, (b) the shaping of the system, and (c) applying the necessary heat to the adjusted system to produce a chewy gel. The shaping may take place before or after either of the other steps of the process. The final products produced in accordance with this process simulate the fibrous texture, chewiness and structure of meats such as pot roast, roast beef, or the like.
In all of these known protein food texturization processes spun or extruded fibers are produced in a coagulating bath, or in a gel system. The fibers then are bound together to imitate the fibrous texture and the mouthfeel of meats. Appropriate flavoring and seasoning agents are added as needed.
An effective texturization technique is needed for texturizing microbial cells, which are distinctly separate particles. We have now discovered a process whereby these distinctly separate particles can be texturized with the aid of a solvent-coagulable texturizing agent.